Telecommunications operators are continuing to develop triple play services which may include the provisioning of high-speed Internet, television/video, and telephone services via a single broadband connection. It is known to use a metro network, also known as a local network, which is a Connection Oriented—Packet Switched (CO-PS) network to provide such services. Technologies such as Multi Protocol Label Switching Transport Profile (MPLS-TP), and Provider Backbone Bridge Traffic Engineering (PBB-TE) have been used in the metro network for this purpose. Up until now such CO-PS networks and the corresponding technology have generally offered the required performance and reliability to satisfy market requirements for triple play services.
Within triple play services the demand for television and video services is increasing. Such television and video services require multicast distribution from a video server to many subscribers which may consume a large bandwidth, and place greater demands on the metro network and underlying technology. These increasing demands have an impact on the ability of telecommunications operators to guarantee the level of service and quality of service that the metro network architecture and technology can offer.
There are many types of protection mechanism that may be used in CO-PS networks to guarantee the level of service and quality of service. Such protection mechanisms aim to provide protection to a network in the event of failures of paths, links or devices within the network so that disruptions to communication services are minimised. A further aim of such protection mechanisms is to avoid loss of traffic in the event of failures within the network.
It is known to provide a redundancy mechanism such as Virtual Router Redundancy Protocol (VRRP) which utilises two edge routers in a core network which are connected to respective edge devices of the metro network. One router acts as a master and the other router operates in a standby condition until required to be used. Such a protection protocol provides protection for traffic passing from the core network to the metro network. The technique delegates protection to the core network at the cost of a complication in redundancy management for the router in the stand-by condition. If a failure is detected in the metro network a fail notification is reported to an edge switching node of the metro network which in turn reports it to the edge router of the core network. This activates protection and starts the sending of traffic towards the standby edge switching node of the core network.
A problem associated with such mechanisms is that they require that a fault in the metro network induces an action or modification in the core network. This is not a straight forward process due to the need for a failure message to propagate from Layer 2 in the metro network to Layer 3 in the core network. Furthermore, using the VRRP the edge switching nodes of the metro network may need to be aware of the master router and be able to modify its traffic forwarding status, or may be required to participate in the router control plane and elect which router is to be used. In addition, when the VRRP is used with an Ethernet tree configuration, each router of the core network is connected to respective edge devices of the metro network, which typically requires two Ethernet worker trees and two Ethernet protection trees to be configured and managed. Overall Layer 3 protocols such as the VRRP add cost and complexity to the metro network which is undesirable.